Spiegelberg, Greg wrote:
This is possible. Below is a brief recipe.
1. Use Veritas Storage Foundation HA with Cluster File System.
2. Have a volume with cfs available to 2 or more systems via SAN.
3. Install PostgreSQL and be sure PGDATA is on the cfs mount
4. Create a Storage Checkpoint of cfs mount (read-write virtual copy)
5. Bring up PostgreSQL on node1
6. Mount storage checkpoint on node2
7. Start PostgreSQL on node2
Drawbacks? Heck yes. There are many and you should understand the
nature of Veritas Storage Checkpoints before using.
Drawback #1-- only works read-only on all but one node. And I am not
even sure what will happen when you start writing on that one node...
I have tested it
though in conjunction with dblink() and some other proprietary API's we
use for load balancing and the potential is there to manage many large
SELECT's.
Ok, but what happens when you start doing inserts, updates, and deletes.
Somehow I think that PostgreSQL's dependance on shmem and semaphores
will cause corruption in your database as soon as you start writing to
it on both nodes. And I don't know enough about PostgreSQL's internal
structure to know if writing on only one node is safe.
Best Wishes,
Chris Travers
Metatron Technology Consulting
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